This invention relates in general to fuel gas analysis and more particularly to an apparatus and method for measuring the Wobbe index of fuel gas, together with the calorific value of the fuel gas.
There are a number of situations in which it is required to make a determination of the Wobbe index of a fuel gas as an indication of the efficiency of that mixture for combustion purposes. The well known Wobbe Index has been defined as the amount of heat released by a burner of constant orifice, McGraw-Hill Dictionary of Science, 1979. It is also desirable in many of these same situations to measure the calorific value of the fuel gas for determination of appropriate billing amounts. The calorific value has been defined as the quantity of heat liberated in a complete combustion of a unit weight or unit volume of fuel, Dictionary of Scientific and Technical Terms, McGraw Hill Book Company, 1974. The Wobbe index is inversely related to the square root of the density of the fuel gas mixture and directly proportional to the calorific value. The measurement of both the Wobbe index and the calorific value of fuel gases is done in a number of conventional systems employing conventional sensors. However, in addition to the obvious requirements of accuracy and reliability of such measurements, speed of response is important, but difficult to achieve.
It is therefore a primary object of the present invention to provide for measurement of Wobbe index and of calorific value of a fuel gas in a system which provides for rapid response time for measuring variations in the fuel. If these measured values are employed in a feedback system to control a process or if the calorific value is being used to provide a billing basis, then it is apparent that this rapid response time renders the entire system more efficient.